WTSC - Commission Meeting
(October 20, 2022) - Improving and Understanding Poly-Drug Information

WTSC - Drug and/or Alcohol Positive Drivers Involved in a Fatal Crash - Revised Statistics

Commissioners heard how methodology changes to improve the identification of poly-drugged driving incidents revealed significant historical overreporting of cases involving cannabis.

Here are some observations from the Thursday October 20th Washington Traffic Safety Commission (WTSC) Commission Meeting.

My top 3 takeaways:

  • Research Associate Max Roberts briefed on “Improving and Understanding Poly-Drug Information,” describing how new analysis of poly-drug traffic fatality data led to a proactive effort by commission staff to revise previous statistics, including on cannabis, aiming to be more reflective of likely impairment (audio - 12m, video, presentation).
    • Roberts said he was sharing the commission’s work “to evaluate and improve our poly-drug data among traffic fatalities” as there wasn’t an established standard. He indicated the commission had been “using the research that's available and making our best judgment as we go through this process” before offering a definition of “poly-drug positive driver” as either a “driver who is positive for alcohol and one or more other drugs as confirmed by toxicology testing, for example testing positive for alcohol and THC, or they can be a driver that is positive for two or more drugs that are not alcohol.”
    • Roberts shared statistics showing “trends in different drug and/or alcohol statuses among drivers in fatal crashes in Washington from 2008 to 2020,” mentioning that the “alcohol only and poly-drug with alcohol categories include any BAC [blood alcohol content] result greater than zero.” This indicated “drivers in fatal crashes positive for one drug only, and no alcohol, has remained relatively consistent over time” and suggested “somewhat of a decline in drivers in fatal crashes that are positive for alcohol only,” he said. “Conversely, drivers and fatal crashes that are poly-drug positive ha[d] been increasing rapidly since 2011 reaching a high of 182 drivers in 2020,” Roberts explained.
    • Staff were engaged in “reviewing positive drug results to better understand impairment and to reevaluate the prevalence of poly-drug driving in Washington,” stated Roberts. He provided a hypothetical example of “an older motorcycle rider waking up on a Sunday morning and getting ready to go for a ride.”
      • “Let's say they woke up and they had some back pain so they took a recommended dose of Tylenol, also known as acetaminophen. They have a couple cups of coffee. They take their daily prescription medication diltiazem to help with their high blood pressure. And let's also say that this person happened to smoke cannabis in the afternoon the prior day. So, on Saturday afternoon…let's say they smoke a cigarette before they go on their ride.”
      • Were the motorcycle rider killed in a traffic collision, a toxicology panel would be “conducted and the results show that this person was positive for five different substances:
        • They test positive for the acetaminophen that they took for their back pain.
        • They test positive for the caffeine in their coffee.
        • They test positive for carboxy-THC [11-Nor-9-carboxy-Δ9-tetrahydrocannabinol], which is the non-active metabolite of the THC they had smoked the day before.
        • They tested positive for their prescription medication, and they tested positive for the nicotine and its metabolite cotinine from the cigarette they smoked before the ride.”
      • Such a case would be “flagged” as a “poly-drug positive driver, and simply looking at the data one might come to the conclusion that it was drug impairment that caused the fatal crash. However, none of these substances or drugs have impairing qualities that actually contributed to the fatal crash. In fact, if we were to remove all of these non-impairing substances we would determine that…drugs and impairment were not actually involved or contributed to the fatal crash. So, we are making an effort to weed out some of these circumstances to get a better understanding of the prevalence of poly-drug positive driving.”
    • Roberts shared criteria used to determine if a substance had a potential for impairment, placing it in ‘impairing,’ ‘potentially impairing,’ and ‘non-impairing’ categories. His examples of non-impairing substances were “caffeine, acetaminophen, and non-active metabolites such as carboxy-THC.” Roberts then explained that WTSC staff were screening out poly-drug toxicological results in cases with:
    • Additionally, there had been a need for “identifying screening versus confirmatory results,” as the former was used to determine “presence of a certain type of drug” and if positive, a “confirmatory test to determine if a specific drug is present, and its levels in the blood or tissue.” Previously, in “some circumstances screening and confirmatory results may be present and counted as multiple drugs,” but officials had begun to “remove the screening result as we already have the…confirmatory evidence.”
    • Poly-drug fatality statistics were revised for “drug positive drivers and fatal crashes from 2015 to 2020,” covering “1,193 drivers in fatal crashes with a positive drug result. There were 125 total unique drugs, and 373 distinct combinations of drugs.” 92 cases were removed “leaving a total of 1,101 poly-drug positive cases,” he told the group, and “the number of unique drugs decreased to 106, and the distinct combinations of drugs decreased to 363.”
    • Perhaps the most dramatic change from applying this method Roberts identified was that “in the beginning data the majority, or 44%, of drug positive drivers and fatal crashes tested positive for two drugs, and only 23% tested positive for only one drug.” After reviewing the cases, officials found “this switched and the majority, nearly 67%, of drug positive drivers and fatal crashes tested positive for only one drug, and 22% tested positive for two drugs.”
    • According to Roberts, from 2015-2020 fatal crashes where alcohol was the only substance present represented “28% of drivers and fatal crashes,” followed by alcohol and THC, “representing 11% of drivers and fatal crashes.” He insisted that “trends and the message remain generally unchanged: poly-drug positive drivers remain the most prevalent group in fatal crashes, and the number of poly-drug positive drivers has been steadily increasing over time.” Roberts further noted drivers in fatal crashes “positive for alcohol increased somewhat in 2020 by eight percent” while “poly-drug positive drivers decreased by 30%, and one drug positive drivers increased by 152% but remained the least common of the three categories.”
    • Roberts made clear that WTSC would continue to apply this method to fatality statistics and planned to release “a larger report in 2023 that covers everything here and much more.” He added that officials and the public could “expect to see some changes to Washington's alcohol and drug positive driving data in the future” before repeating that the “overall trends and message remain generally unchanged.”

Information Set